This invention relates to switching devices which may be constructed as a plurality of assembled units that are manually actuable to operate electrical switching means in each unit. As a result of the operation of the switching units, appropriate corrections are made to electronic instruments for whatever purpose is required.
Many of the switching devices presently employing electrical switching means utilize thumb-wheels, such as star wheels or serrated wheels, having indicia printed on a cylindrical rim, on protrusions, in grooves, or in between serrations on the periphery of the thumb-wheels. The thumb-wheels are rotatably mounted in an apertured switch case so that an indicium on the thumb-wheel may be viewed through the aperture. These thumb-wheels are rotated by the user's finger pressing on protrusions or serrations on the periphery of the thumb-wheel. As the thumb-wheel is rotated, electrically conductive wipers mounted on the thumb-wheel rotate and contact various electrical contacts, thereby forming various electrical circuits corresponding to the indicium appearing on the thumb-wheel through the case aperture.
It has become apparent through the use of such thumb-wheel switches that a more accurate and less tiring type of switch is desirable where frequent settings of the switch are required. The user of these thumb-wheel switches, in order to rotate the thumb-wheel, usually covers the indicia on the periphery of the thumb-wheel with his finger. Such covering of the indicia makes it difficult for the user to accurately position the thumb-wheel in order to quickly form the desired circuit. This affects both the accuracy of the thumb-wheel switch and the rapidity with which the various circuits corresponding to the indicia can be completed. Further, the finger of the user, after frequently operating a thumb-wheel switch for a number of hours, becomes tired due to the pressure required to rotate the thumb-wheel. Also, the pad of the user's finger usually becomes sore due to frequent contact with the protrusions or serrations on the thumb-wheel. This impairs the user's efficiency and thus the efficiency of the switch.
We have discovered that by providing a lever actuated switch interconnected with an indicia-carrying switch wheel, the accuracy and speed of operation of such an electrical switch can be improved to a considerable extent. Also, the comfort of the frequent user of the switch can be improved.